Response of Drought Tolerant and Conventional Corn to Limited Irrigation

The purpose of this study was to evaluate the response of two commercial hybrids (DKC 62-27 DGVT2PRO [drought tolerant trait (DT)] and DKC 62-98 VT2PRO [conventional]) to limited irrigation. Preliminary results from the 2014 and 2015 growing seasons at Southwest Research-Extension Center near Garden City, Kansas, indicate the effect of irrigation capacity on corn yield was significant (P \u3c 0.001) for both hybrids. The effect of the drought tolerance trait on yield was not significant (P \u3e 0.05) in both years. The effect of the interaction between irrigation capacity and corn hybrid on yield was also not significant (P \u3e 0.05). Hybrid type had a significant effect on crop water use (P \u3c 0.05). Crop water use ranged between 25.1 to 15.2 and 26.0 to 15.1 inches for the conventional and DT corn hybrids respectively. Averaged across treatments, the DT hybrid used approximately 3% more water compared to the locally adapted hybrid. It is worth noting that since the two hybrids were not isolines, any differences in crop water use could be attributed to differences in genetics and not the drought tolerant trait. The effects of the drought tolerant trait on water productivity were not significant in both years (P \u3e 0.05). Water productivity ranged between 10.9 to 3.6 and 11.2 to 5.6 bu/a/in for conventional and DT corn hybrids, respectively. As expected, DT and conventional corn hybrids had curvilinear yield response to irrigation and linear response to seasonal crop water use/evapotranspiration (ETc). The marginal water productivity for conventional and DT hybrids ranged from 18.4 to 14.5 bu/a/in and from 15.2 to 14.6 bu/a/in respectively. These preliminary results indicate no signifi­cant differences in yields and water productivity between DT and conventional hybrids under full and limited irrigation. More research is needed to confirm these findings

Sorghum Yield Response to Water Supply and Irrigation Management

Grain sorghum yield, under full and limited irrigation, was evaluated at three locations in western Kansas (Colby, Tribune, and Garden City). The top-end yield under full ir­rigation was 190 bu/a. However, there were no significant differences among irrigation treatments at all the three locations due to the above normal rainfall received during the 2015 growing season. These preliminary results indicate that there is potential to improve grain sorghum yields under limited irrigation. Additionally, best management practices to maximize kernels per head could have the greatest effect on grain yields

Response of Drought Tolerant and Conventional Corn to Limited Irrigation

With declining water levels in the Ogallala aquifer, many wells cannot supply peak irrigation water needs for corn. Emerging drought-tolerant (DT) corn hybrids could help farmers maintain yield with limited capacity wells. A knowledge gap exists comparing transgenic DT and conventional corn hybrids in yield response to water level. The purpose of this study was to compare yield, yield components, water productivity, and irrigation water use efficiency response of DT corn with cspB (DKC 6267 DGVT- 2PRO) transgene trait and conventional corn hybrid (DKC 62-98 VT2PRO) with similar maturity to full and limited irrigation. Preliminary results from the 2014 growing season indicate the effect of irrigation level on corn yield was significant (P-value \u3c0.001). The effect of the cspB transgene trait in the DT hybrid did not affect yield (P-value=0.32), and there was no effect of the interaction between irrigation level and corn hybrid on yield (P-value=0.82). The effect of irrigation and hybrid on 100 kernel weight was significant, with P-value\u3c0.001 and P-value\u3c0.001 respectively. The 100 kernel weight is a measure of kernel size, and was higher for the conventional hybrid compared to the DT hybrid

Irrigation Scheduling Based on Soil Moisture Sensors and Evapotranspiration

Irrigation scheduling is crucial to effectively manage water resources and optimize profitability of an irrigated operation. Tools that can be customized to a field’s characteristics can greatly facilitate irrigation scheduling decisions. Soil moisture sensors and the evapotranspiration (ET)-based KanSched are two of the tools that could be implemented in an irrigated farm. Focusing on the installation of soil moisture sensors, demonstration set-ups were established at the Southwest Research-Extension Center plots in Garden City, Kansas, and in a producer’s field, each with three types of moisture sensors at different depths. Among others, this project validates the importance of moisture sensors being installed as early as possible in a representative location with good soil-sensor contact. The moisture sensors, at the least, help in determining when irrigation water should be applied or scheduled. Furthermore, in implementing an irrigation schedule, the irrigation manager considers the irrigation system capacity, the amount that can be efficiently applied, the soil intake rate, and other relevant factors

Determining Profitable Annual Forage Rotations

Producers are interested in growing annual forages, yet the region lacks proven recom­mended crop rotations such as those for grain crops. Forage production is important to the region’s livestock and dairy industries and is becoming increasingly important as irrigation well capacity declines. Forages require less water than grain crops and may al­low for increased cropping intensity and opportunistic cropping. A study was initiated in 2013 comparing several 1-, 3-, and 4-year forage rotations with no-till and minimum-till (min-till). Data presented are from 2013 through 2015. Winter triticale yields were increased by tillage. Double-crop forage sorghum yielded 23% less than full-season for­age sorghum across years. Oats failed to make a crop in 2013 and do not appear to be as drought tolerant as spring triticale or forage sorghum. Subsequent years will be used to compare forage rotations and profitability

Mobile Drip Irrigation Evaluation in Corn

Mobile Drip Irrigation (MDI) involves attaching driplines to center pivot drops. MDI has potential to eliminate water losses due to spray droplet evaporation, water evapo­ration from the canopy, and wind drift. MDI also may reduce soil water evaporation due to limited surface wetting. A study was conducted with the following objectives: 1) compare soil water evaporation under MDI and in-canopy spray nozzles; 2) evalu­ate soil water redistribution under MDI at 60 inch dripline lateral spacing; 3) compare corn grain yield, water productivity, and irrigation water use efficiency; and 4) compare end-of-season profile soil water under MDI and in-canopy spray at two well capaci­ties 300 and 600 gpm. The experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, Kansas. The experimental design was randomized complete block with four replications, and two treatments MDI and in-canopy spray nozzles. Soil water evaporation was measured using four-inch mini-lysimeters placed between corn rows. The effect of a 60-inch lateral spacing on soil water redistribution was evaluated using soil water measurements made using neutron attenuation to a depth of 8 feet. Preliminary results indicate soil water evaporation was lower under MDI compared to in-canopy spray nozzles, by 35% on average. Soil water redistribution was adequate for dripline spacing of 60 inches in silt loam soils of south­west Kansas. At 600 gpm well capacity, corn yields were 247 and 255 bu/a for MDI and in-canopy spray nozzles, respectively. At 300 gpm well capacity, yields were 243 and 220 bu/a for MDI and in-canopy spray nozzles, respectively. However, the differences were not significant (p \u3e 0.05) between the irrigation application technologies in 2015. The effect of application method on water productivity and irrigation water use efficiency was also not significant. The lack of significant differences could be attributed to the above normal rainfall received during the 2015 growing season (18.3 inches from May to October). Normal mean annual rainfall for the study area is 18 inches. The effect of application method on end-of-season soil water was statistically significant under low well capacity (300 gpm) with Mobile Drip Irrigation having more soil water compared to in-canopy spray nozzles in the 8 foot profile at harvest. It is worth noting that plots under MDI did not have deep wheel tracks associated with sprinkler nozzles

Mobile Drip Irrigation for Water Limited Crop Production: Initial Results

The farmers within the Ogallala aquifer desire to extend the usable life of this aquifer despite experiencing diminishing well capacities, thus the quest for more efficient irrigation application technologies. Mobile drip irrigation (MDI), which integrates drip lines onto a mechanical irrigation system such as a center pivot, has attracted their attention lately. The concept is that by applying water along crop rows, it was hypothesized that MDI could eliminate water losses due to spray droplet evaporation, wind drift, and reduce soil evaporation due to limited surface wetting especially before canopy closure. A study was conducted with the following objectives: 1) compare soil water evaporation under MDI and in-canopy spray nozzles (low elevation spray application (LESA)); 2) evaluate soil water redistribution under MDI at 60-inch drip line lateral spacing; and 3) compare corn grain yield, and water productivity under MDI and LESA at two well capacities (300 and 600 gpm). The experimental design was randomized complete block with four replications and two treatments (MDI and LESA). Nozzle performance was evaluated using the Spot-on flow measurement device. Soil water evaporation was measured using 4-inch mini-lysimeters placed between corn rows. The effect of a 60-inch lateral spacing on soil water redistribution was measured using neutron attenuation to a depth of 8 feet. Corn yield was determined from harvesting two 40-foot corn rows in the center of each plot. Measured and design nozzle flow rates were similar indicating the irrigation system was performing as designed. Results indicate that soil water evaporation was lower under MDI compared to LESA by an average of 35%. Soil water was greatest at the mid-point between two drip line laterals spaced 60 inches apart at a depth of approximately 20–24 inches. These results indicate drip line spacing of 60 inches is adequate for silt loam soils of southwest Kansas. The effect of irrigation application method (MDI versus spray nozzles [LESA]) on yield at high (600 gpm) and low (300 gpm) well capacities was not statistically significant at the 5% level (P \u3e 0.05). The effect of application method on water productivity and irrigation water use efficiency was also not significant. The lack of significant differences in yield could be attributed to the above normal rainfall received during the 2015 growing season (18 inches from May to September). However, it is worth noting that the effect of application method on end-of-season soil water was statistically significant under low well capacity (300 gpm) with mobile drip irrigation having more soil water compared to spray nozzles

Fallow Replacement Crop (Cover Crops, Annual Forages, and Short-Season Grain Crops) Effects on Available Soil Water

Producers are interested in growing cover crops and reducing fallow. Limited information is available on growing crops in place of fallow in the semiarid Great Plains. Between 2012 and 2015, spring cover, annual forage, and grain crops were grown in place of fallow in a no-till wheat-grain sorghum-fallow (WSF) rotation in southwest Kansas. Growing a cover, hay, or grain crop in place of fallow reduced the amount of stored soil moisture at wheat planting. On average, cover crops stored slightly more moisture than hay crops, but this soil moisture difference did not affect wheat yields. Soil moisture after grain crops was less than after cover or hay crops, and this difference resulted in reduced wheat yields. These results do not support claims that cover crops increase soil moisture compared to fallow. Soil moisture storage from fallow crop termination to wheat planting was greatest among those treatments that were most dry at termination and produced the most aboveground biomass. On average, cover crops had a 28% precipitation storage efficiency (PSE) and hay crops had a 22% PSE between termination and wheat planting. Fallow during the full-fallow period (sorghum harvest to wheat planting) had an 18% PSE. Crops grown in place of fallow must compensate for the expense of growing the crop plus the reduction in soil moisture for the next crop

Forage Sorghum and Corn Silage Response to Full and Deficit Irrigation

There is limited information on forage sorghum and corn silage yield response to full and deficit irrigation in Kansas. The objective of this study was to generate information on forage sorghum (brown mid-rib hybrids (BMR and non-BMR)) and corn silage yield response to different levels of irrigation as influenced by irrigation capacity in southwest Kansas. Preliminary results indicate the effect of irrigation capacity on forage yield was significant (P = 0.0009) in 2014 but not 2015, probably due to high growing season rainfall received in 2015. Corn silage produced significantly (p \u3c 0.05) higher biomass at all irrigation capacities compared to forage sorghum hybrids in 2015. BMR forage sorghum produced significantly lower biomass compared to non-BMR hybrid in both 2014 and 2015 (P \u3c 0.05). The highest amounts of forage produced for corn silage, BMR, and non-BMR forage sorghum were 24.6, 17.4, and 21.1 tons/a adjusted to 65%, moisture respectively. Water productivity ranged from 1.0 to 1.4 dry matter tons/a/in. More research is needed under normal and dry years to quantify forage sorghum and corn silage yield and forage quality response to full and deficit irrigation

Exploring the Value of Plant Analysis to Enhance Water Use Efficiency in Southwest Kansas

Nutrient deficiency is identified by use of visual symptoms. However, the application of the proposed deficient nutrient often does not result in the correction of the observed visual symptoms. This is because essential nutrients do not operate independently of each other or independently of the overall plant health and growing conditions. A study was initiated in 2016 at the Kansas State University Southwest Research-Extension Center Finnup Farm near Garden City, KS, to use both soil and plant analyses to identify toxicities or hidden deficiencies that could be limiting corn yield at various irrigation capacities. Soil samples prior to planting and plant samples at tasseling were collected from corn grown under five irrigation capacities and dryland conditions. Irrigation capacities were 0.25, 0.17, 0.13, 0.10, and 0.08 in./d. Relationships among plant nutrients and corn yield were developed to identify possible nutrients that could be limiting corn yield. Soil analysis showed soil pH of around 8 and organic matter of around 2%. In general, as expected, soil pH did increase with reduction in irrigation capacity. Sulfur (S) was the only nutrient found to be of concern within the soil analysis. Sulfur was also found to be of concern in the plant analysis. The S concentration was right at the lower limit of the sufficiency level. All other nutrients were within the required sufficiency level. However, manganese (Mn) (110 ppm) concentration was found to be higher than that of iron (Fe) (94 ppm). Whenever Mn concentration in a plant is higher than that of Fe regardless of concentration, it is an indication of Fe deficiency. Moreover, a significant relationship (P = 0.05) was observed for plant Fe concentration and corn grain yield at the 10% significance level. Likewise, an even stronger significant relationship (P = 0.035) was observed for Fe/Mn ratio and corn grain yield at the 5% significance level. These results suggest that Fe deficiency could be the hidden deficiency limiting corn yield